Dissolved Gas Analysis

Over time, a transformer’s insulating materials and electrical equipment begin to degrade, dissolving gases into the unit’s oil. The rate and distribution of these generated gases ultimately leads to transformer failure. We’ve listed the six most common DGA results, and the corresponding solutions that will extend the life of your equipment.

1. High carbon monoxide content observed in the DGA

   Probable cause: Inefficient cooling, overloading
   Solution: Inspect the cooling system, replace the pump and/or valves

2. High oxygen content observed in the DGA
   Probable cause: Worn gaskets
   Solution: Inspect for potential arcing or corona, replace the gaskets

3. High ethylene, methane, and/or ethane content observed in the DGA
   Probable cause: Overheated or worn load tap changer (LTC) contact
   Solution: Check the LTC operation, inspect and replace the LTC contact

4. Low levels of acetylene observed in the DGA
   Probable cause: Short in the oil pump motor
   Solution: Inspect and replace the LTC contact and motor; check for arcing, overloading

5. High moisture content observed in the DGA
   Probable cause: Worn or faulty gaskets, leaking air cell, spent desiccant, overloading
   Solution: Inspect gaskets, air cells and silica gel; replace necessary parts

6. Acetylene detected in the LTC oil DGA
   Probable cause: Vacuum bottle failure, arcing
   Solution: Inspect and replace the faulty vacuum bottles
   

Transformer Oil

Transformer oil is used for its chemical properties and dielectric strength, acting as an insulator/ cooling agent. It should be tested periodically to prevent costly downtime.

We’ve listed eight common problems with oil test results, levels and accumulation, and corresponding parts to extend the life of your transformers. 

1. Oil contamination from the main tank into the LTC (migration)
   Probable cause: Faulty seal between the LTC compartment and the main tank
   Solution: Inspect and replace the tap board and gaskets
2.  Oil temperature alarm, no oil flow alarm, and/or tripping fan motor 
   Probable cause: Faulty temperature switch, failed oil pump and/or motor, failed fans
   Solution: Inspect and replace the temperature gauge, pump, pump motor and fans
3. Oil accumulation in/around the control cabinet
   Probable cause: Gasket leaks 
   Solution: Inspect and replace gaskets
4. Bushing oil level is low 
   Probable cause: Overheated gaskets  
   Solution: Inspect and replace the Bushing/bushing gaskets

5. Low oil level and/or leaks
   Probable cause: Faulty gaskets, overloading
   Solution: Inspect and replace the all gaskets on the main tank

6. Contaminated oil
   Probable cause: Faulty oil pump
   Solution: Inspect oil pump for leaks, replace if necessary

7. Low oil level for the sealed conservator system
   Probable cause: Overloading, failing radiator
   Solution: Inspect and replace the radiator valves and gaskets

Gauges and Alarms

The transformer’s gauges and alarms monitor and alert to various vitals, such as oil level, oil and winding temperatures, pressure or vacuum in the tank, oil flow and more. 

We’ve listed three common gauge and alarm issues and the corresponding solution to extend the life of your transformers.

1. Inaccurate gauge operation
   Probable cause: Cracked face or glass, stuck needle
   Solution: Inspect and replace affected gauges
2. Pressure vacuum gauge at zero
   Probable cause: Check the gauge operation
   Solution: Inspect and replace the pressure vacuum gauge
3. Nitrogen pressure alarm
   Probable cause: Faulty gaskets; check the nitrogen bottle
   Solution: Inspect and replace the pressure vacuum gauge

Power and Voltage

A transformer’s power and voltage are defined by the amount needed to keep equipment running properly. Fluctuations in these can lead to incorrect diagnosis, accessory failure or unit failure. We’ve listed two potential issues and the solutions to them.

1. Capacitance increases and/or there is abnormal tap voltage
   Probable cause: Cracked face or glass, stuck needle
   Solution: Inspect and replace affected gauges
2. The power factor is increasing
   Probable cause: Check the gauge operation
   Solution: Inspect and replace the pressure vacuum gauge

Other Concerns

If your transformer’s problem is not listed, please call us at 800-727-8443 to speak with our technical specialists. 

1. Non-OSHA approved fan guards
   Probable cause: Inspect fan guards to ensure they meet OSHA standards
   Solution: Replace fan guards
2. Abnormal number of LTC operations
   Probable cause: Defective LTC control
   Solution: Inspect mechanical control components, replace the LTC control

*For more information, please print out our troubleshoot guide.